I've received an update from the dealer today, after they spoke with Mazda and they agree it seems to be the app causing the alarm to trigger. I'm going to disconnect the app and see what happens.
I've seen (heard!) the alarm trigger when not charging. One of the questions Mazda asked me, via the dealer, was whether I had interacted with the app shortly before the alarm was triggered. Of course most people interact with the app when they are charging so this may have been a red herring. Let's hope Mazda come up a solution.I've managed to trigger my alarm today when stopping the climate control via the app. The car was not plugged in, so I think my issue is more related to the app starting the alarm than the car.